The fabrication of electronic devices has been carried out using photolithography process in conjunction with epitaxial growth techniques such as molecular beam epitaxy (MBE), metallo-organic chemical vapor deposition (MOCVD), liquid phase epitaxy (LPE) and isothermal vapor phase epitaxy (ISOVPE). These techniques have capability of producing multicomponent semiconductor epitaxial films with good radial compositional uniformity, surface morphology and electrical properties. However, the techniques suffer from several drawbacks such as expense, toxic waste, slow growth rate, skilled labor requirements, difficulty in controlling multi-elements in the film and requirement of sophisticated and expensive UHV equipment
The direct printing technique is an inexpensive alternative to conventional vacuum deposition and photolithographic process.
Previous efforts of fabrication of electronic devices using ink jet printing are limited to polymer inks and inks having a few selected metals, such as tin, copper, silver, and gold.
Direct printing techniques have attracted considerable attention as an alternative to conventional vacuum deposition and photolithographic processes. Various functional films such as gate electrodes, gate dielectrics, source and drain contacts and active semiconductor layers have been printed recently.
Industry estimates project that printed electronics will be 35 percent of a $1.92 billion printed, thin film and organic electronics market. By 2020, the market could grow to $55.1 billion, with 71 percent printed electronics. While the development of printed electronics is in the early stages, it is evident that it has the potential to change the electronics industry.
The direct printing processes include micro contact printing (μ-CP), nanoimprinting, solid state embossing, screen printing, drop-on-demand (DOD) inkjet printing and laser induced forward transfer (LIFT). Varieties of devices, such as RFID tags, LEDs, organic solar cells, organic thin-film transistors, and biomedical devices, have been fabricated using direct printing techniques showing the tremendous advancement in last few years.
Among all direct printing techniques, inkjet direct writing has emerged as the most attractive because of the ability of fully data driven and maskless drop-on-demand (DOD) inkjet processing. The key element of ink jet processing is to formulate inks and precursors that can be sprayed or printed with desired materials of proper composition and morphology and optical and electrical properties. So far, inkjet direct writing is limited to conducting polymers, tin, copper, silver and gold.
Currently, only metal based ink is commercially available. Examples of the metal based inks are Metalon JS-011 and JS-015 inks of Novacentrix, Ag 50P, Ag 60N and Cu NPs-based inkjet inks of Samsung ElectroMechanics, IJ 242-54 ink of Cima NanoTech.
Examples of metal ink patents are Kamikoriyama, et al. “Nickel ink” U.S. Pat. No. 8,012,378, Asada et al. “Silver-coated ball and method for manufacturing same” U.S. Pat. No. 8,039,107, Zurcher et al. “Metal inks, methods of making the same, and methods for printing and/or forming metal films” U.S. Pat. No. 8,066,805, Rockenberger et al. “Metal inks for improved contact resistance” U.S. Pat. No. 7,977,240, Chung et al. “Conductive inks and manufacturing method thereof” U.S. Pat. No. 7,955,528, Li et al. “Manufacture of thin solar cells based on ink printing technology” U.S. Pat. No. 8,071,875 and Wu et al. “Semiconducting ink formulation” U.S. Pat. No. 8,052,895.
Needs exist for new formulations and inks are required to realize the full potential of inkjet printing for manufacturing the inexpensive electronic devices.